1. Field of the Invention
The invention generally relates to the field of spectrum analyzers, and more particularly to a mobile device which analyzes multiple bands of RF frequencies.
2. Background
Wireless networks operating under standard IEEE 802.11, also known as Wi-Fi, are wireless local area network (WLAN) technology commonly used for networking computers together. Wi-Fi can operate in either the 2.4 GHZ Industrial Scientific Medical (ISM) band, or in the 5 GHz band. The 2.4 GHz band is roughly 100 MHz wide. Within that band there are 14 channels that are 22 MHz wide. Due to frequency constraints in the 2.4 GHz ISM band, these Wi-Fi channels overlap each other. The 5 GHz band is 600 MHz wide with 25 channels. Also, the 2.4 and 5 GHz bands share frequencies with a number of other users such as cordless telephones, Bluetooth® devices, ZigBee® devices. To the 802.11 WLAN devices, these other devices may be viewed as interferers. These potential interference sources may cause difficulty with network communications.
When setting up a wireless network or troubleshooting network problems, it is necessary to learn what portions of the available radio frequencies, or bands, are free of interfering signals. The test instrument most commonly used for such a task is the spectrum analyzer. A spectrum analyzer scans, or ‘sweeps’ the desired range of frequencies, then normally plots the strengths of the signals received in the vertical axis against the scanned frequencies on the horizontal axis. The result of such a sweep is shown on a graphic display to enable a user to graphically see the spectrum that is analyzed. Spectrum analyzers are specialized test instruments that often cover broad ranges of frequencies. Conventional spectrum analyzers focus on features that enhance the accuracy of measurements, such as: sweep time, principles of the invention, resolution bandwidth and frequency range. These features often require specialized hardware. For instance, conventional spectrum analyzers typically contain dedicated hardware capable of quickly taking precise measurements. This specialized hardware is typically bulky and cost prohibitive for a small scale user, such as a small business, a personal computer user, or highly mobile technical support personnel. Conventional spectrum analyzers also lack certain spectrum display and data manipulation features, creating additional work for a user desiring a particular display or spectrum data manipulation. For example, conventional spectrum analyzers typically graph amplitude versus frequency, requiring users to mentally map channels utilized by devices onto the frequency axis. Furthermore, while conventional spectrum analyzers allow an image to be saved, the image is generally only a representation of a single instant in time.
Consequently, it would be desirable to provide a portable and inexpensive device for portable analyzing and troubleshooting the Wi-Fi spectrum.
U.S. Pat. No. 7,459,898 to Woodings discloses a System and Apparatus for Detecting and Analyzing a Frequency Spectrum. The apparatus is suitable for spectrum analysis in the 2.4 GHz radio frequency band. The apparatus is a small device that plugs into an available Universal Serial Bus (USB) port of a computing device such as a laptop computer. The result is a highly portable system that includes a 2.4 GHz radio system and hardware to support USB communications. The apparatus together with its companion software, which runs on the connected computer, functions as a spectrum analyzer. The software and the hardware apparatus are operated from the computer's graphical user interface (GUI). GUI's are a standard part of modern computer operating systems such as the common Microsoft® Windows operating systems.
What is needed is a small, portable, and inexpensive device that will perform spectrum analysis on at least the 2.4 and 5 GHz radio frequency bands. The device should work with a computer that has a GUI, and ideally existing software capable of spectrum analysis and display should be utilized.